Detonating or impact fuse



July 27, 1948. H. J. NICHOLS DETONATING OR IMPACT FUSE Filed Nov. 7,1939 iigji 7 0 j l hl Ir, E

Patented July 27, W48

UNITED STATES PATENT OFFICE 7 Claims.

This invention relates to detonating or impact fuses especially foranti-aircraft or anti-tank projectiles and the like.

Detonating fuses for small anti-aircraft projectiles, for example, offernumerous difficulties because of their small size and the greataccelerating and rotary forces to which the parts are subjected infiring and in flight. Yet it is necessary that fuses for this purpose beextremely sensitive on impact, and at the same time be entirely safe instorage, handling, and firing. Because of the force of set-back on firinsome projectiles, the detonator may be fired by concussion on firing.This makes a bore-safe feature highly desirable. A fuse to be boresafemust have adequate provisions against arming in the bore of the gun, andin the event the detonator is exploded by concussion, provision must bemade against the burster charge of the projectile being exploded and thepresent invention accomplishes this. A further desirable feature is thatthe fuse be not armed until the projectile has travelled some distancebeyond the muzzle of the gun, since a strong retarding force occurs whenthe projectile strikes the air on emerging from the gun, and if thesensitive firing elements can co-act, premature firing may result. Toinsure sufiicient sensitivity on impact with light targets, such as thewings of aircraft, the firing element must be of light weight. To obtainboth super-sensitive and super-quick action, special provision should bemade that the firing pin first strike the target, and as this element isthereby retarded, the projectile collides with the firing pin, producingdetonation before the projectile has been sensibly retarded. In

order to insure certain arming action and sensitivity, it is highlydesirable that the arming and firing elements be virtually dynamicallybalanced with respect to the axis of rotation of the projectile, sinceotherwise the high rate of rotation of the projectile in flight willproduce undesirable unbalanced forces tending to interfere with theintended action and sensitivity.

Finally, from the practical standpoint, fuses of this class should havefew parts, be simple in construction, easily loaded and assembled, andadapted to low cost manufacture in large quantity.

It is therefore one of the principal objects of this invention to meetin a highly eficient, reliable, and practical manner thegeneral. andspecial requirements above stated.

Another object is to provide simple and rugged arming means whichutilize forces genings erated by the firing process to effect arming inpart, complete arming being dependent upon the action of supplementarykinetic means.

Another object is to provide means for extending the impact firingelement after the projectile is in flight.

Another object is to provide a high degreev of safety against prematureexplosion in handling the fuse, or on firing the loaded and fusedprojectile.

Another object is to provide a novel tive bore-safe feature.

Other objects will in part be obvious from the annexed drawings and inpart hereinafter indicated in connection therewith by the followinganalysis of the invention.

This invention accordingly consists in the features of construction,combination of parts, and in the unique relation of the members and inthe relative proportioning and disposition thereof, all as morecompletely outlined herein.

To enable others skilled in the art fully to comprehend the underlyingfeatures of this invention, that they may embody the same by thenumerous modifications in structure and relation contemplated by theinvention, drawings depicting a preferred embodiment of the inventionform a part of this disclosure, and in such drawlike characters ofreference denote corresponding parts throughout the several views, inwhich- Fig. 1 shows in longitudinal section a pointimpact, detonatingfuse according to the invention, the mechanism being shown in unarmed orsafe condition. l

Fig. 2 is a similar section, showing the mechanism in armed condition orits condition immediately after being fired.

Fig. 3 show a bottom View of the fuse.

Fig. 4 shows in section details of the rotor or detonator holder takenon 4-4 of Fig. 2.

Fig. 5 is a perspective detail of the spring support.

Referring to these drawings, and especially Fig. 1, the fuse casingincludes a body ll! of rugged proportions with external screw threads IIat the base end l2 for assembly to the projectile not shown. At thebottom is an internally threaded cavity I3 in which a loaded booster cupl4, containing pressed tetryl or the like, is secured by means of athreaded ferrule IS. The tetryl is covered by a paper disc l6 forprotective purposes. The point end I! of the fuse body I0 is providedwith an internally threaded cavity 18 adapted to receive the nose piece20 which forms and effecpart of the fuse casing. Rearwardly of thethreaded cavity I8 is a cavity 2| specially shaped to receive the rotor22 or detonator holder to be described and to cause said rotor at alltimes to rotate with the projectile when the latter is fired. Because ofits shape, this cavity is preferably formed by forging or casting.Extending from the rotor cavity 2|, to the booster cavity is a smalldiameter axial hole 24, counter bored at the upper end to receive asmall metal cup 25, called the cord protector cup. The interior of thecup and the axial hole are filled with tightly compressed tetryl or thelike, this part of the' detonating train being termedithedetonatingcord. The purpose of the protector cup 25 is to protect the end of thecord frommoisture, and also from hot gases likelyitolbe. generated inevent of premature explosion of the detonator 26, carried by the rotor22.

The rotor 22 is centro-symmetric, that is, it is symmetric twithrespectto..its. center of mass. Consequentlygit is staticallybalancedwith respect to any axis passing through'its center. Il- -lustratively,such a rotor, may take the form of a right-circular cylindricalmemberdisposed edgewise in the rotor cavity 2|, with itsaxis transwerseto the axisof the. fuse body. By .virtue of iitsl specialshaping-aforesaid, the rotor cavity, -for the right circular cylindricalrotorillustrated, is provided with a cylindrically curvedbottom--portion and with planeend walls against. which the end faces of therotor seat. Accordingly, the rotor m'ay turnrelatively to the fuse bodyon its own axis, but is constrained by engagement of its end-iaces 1Withthwend walls of. the .cavity to at all times rotate Withthe-fuse andprojectile --when the latter is fired.

Midway of its ends. the v'rotorl has adiamfetral roundhole adapted toreceive the cywlin'drical detonator capsule..26. The. detonator capsulepreferably is a .thin drawn copper shell, in which the highlycompressedfulminate= deto- "nating charge is loaded. Therassemblyof .the detonatoris completed by covering the fulminate -charge, loadednot quite to thetop, by athin disc 27 acemented in placeby a water-proof cement. Whenthe-detonatorcapsule' 26 is loaded into the rotors it is coated wthaistrongadherent cement "to hold the capsule-securely:in place in.the rotor 22.Therotonis provided with a small :tapered hole 28 (Fig. 2) located at anangle 45-ormore -td-the axis of thei detonator i26,.this hole beingadapted to receivethe: point 30 ofithe firing pin 6 |-When the rotorisin the safeiposition as shown in Fig. 1.

In addition to the rotor .22 being formed so that it is virtua-llystatically-balanced with respect to its axis, it is also so constructedthat in its assembled-position and priorto arming,'it is*dynamically-unbalanced with respect-to the axis of the fuse, which'islikewise substantially the alaxis ofrotation of the projectileaccordingly, and referring to Fig. 4, on each end of the rotor 222- a-'central channel 32 is cut at an inclination mfsay *to the axis ofthe-detonator 26. This leaves two lands 33 on each end of the rotorin"the 'form of segments contained within the cir- -cular-section of therotor, each-subtending an larc ofapproximately-120; which segments pro-"duce the dynamic unbalance. FThe unbalanced areas are indicated by theportionsbetween the dotted'lines and:peripheryin Fig. 2. There is also'some -minor unbalance due to the detonator hole andits contentsg butbecause of the rela- 11 tively -small r diameter" of 'this hole and thepo- "The firing pin, having a sharp pointed inner end .:3|I.and arounded head 3'! extending outside the nose piece 20, is larger indiameter at the head -of-its shank,-which shank is circled by a groove..38 (Fig. 2). .Thenose piece 20 and spring support 34 maintain thefiring pin 3| in position in the-axis of the fuse. The nose piece axialhole is counter-bored from.the inner end to provide a barrel '40 :inwhichvworksa small setback ring .4.|,'also the extender springi=36. ,Thetopwcoil 36c of the extender spring;36-is of smalleridiameter than theother coils, and fits snuglyintojthe gIO0Ve:'38 in the firing pin shank3|.'

The various .threadedzparts of the fuse;arelassembled by spannersengaging recesses :39 was shown in .Fig. 1. ';.Then-..the. operation isas follows: On firing,.-. all partstend to move away .from the. point 31by reason of. the acceleration of firing; termed :fset-back.The'set-back. ring 4|: and extender-spring 3B; .are..aife'cted by-:;thisforce, and thetop coil 360 of the spring .is forced out of thegroo.ve.:3|l in .the'firing.pinsshankaiil, due to the.=inertia of thering and of the spring itself; and moves rearwardly ;until .thecollfl36c rests below. the taperedlshoulderi 42; ofthe-firing pin. The..firing, pin 30, supported. by-aitshead 31, remainsin the hole in therotor=22, preventing the. rotor: from rotating, although the set-backforce onthe rotortisnormallyiadequate to prevent'rotation of the rotorwhile the projectile is in the bore. of the. gun.

.It .should" be noted. here that; int event ;the detonator 261'sexploded by theconcussion of .fir-

.ing, the rotor. 22 :is being pressed against .the bottom of the rotorcavity 2l-with great pressure, and the effect of .the:detonatorexplosionwill be to wedge a plug of metal from the rotor into, the top:ofithe. axial cord' hole1124, securely sealing ..same.against'.the'entryofhot gases. ;The. cord protector cup 25 will shieldthe tetryl cordfrommechanical shockwto adegree sufiicientto,- preventzshockdetonation. Thegases from the-adetonatorwill :expandintothe voidsiin thefuse, the set.back force sufiicingyto. preyentrexpulsmn of the firing pin.

Referring nowsto 2, as the :projectlle leaves the-muzzle .of the gun andthe forcegof the. propellant becomes. spent, the acceleration -of.theprojectile :ceases, and: deceleration: .due .to

the air resistance occurs. 3 At this instantwthe extender spring? 36.advancesthefiring. .pin 30 to extended position as shown in Fig. 2. Therotor iS'l'lOW freed;.of the restraint of the firing pin r 30 and theset-back force; and at the same time the rotation. of .:theprojectile'due to. firingds a maximum. Thus ithe=.,dynamic unbalance ofthe rotor 22 takes effect and causes the rotor torotate.the':detonator:.26.into axial; position as shown. "The fuse isnow completelyarmed (at somedistancebeyondthe muzzlecf the guntand onstriking the .target,-, even though thee-target abe. a flimsyone,=-suchas the. wing fabricbf an airplane;v thethead' {31 of the.firing -pin will -en-.

counter substantial resistance and will be checked in flight. Theprojectile will then relatively drive the detonator 26 into the firingpin 30, instantly detonating the former. The wave of detonation willtravel through the tetryl cord 24 and booster charge [4 to theprojectile burster or high explosive charge (not shown) but of standardconstruction. The detonation wave travels so rapidly that the projectilewill burst within a few inches of the point of encountering the target.As is well known to those versed in this art, the firing point 30 ismade sharp, and the top layer of the detonator charge is of particularlysensitive composition to promote sensitive firing action.

It will be evident that the invention provides novel and advantageousfeatures and adequately meets the general and special requirements forzfuses of this class.

Without further analysis the foregoing will so fully reveal the gist ofthis invention that others can, by applying current knowledge, readilyadapt it for various applications without omitting certain featuresthat, from the standpoint of the prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of the invention, andtherefore such adaptations should and are intended to be comprehendedwithin the; meaning and range of equivalency of the following claims.

I claim:

1. In afuse of the class described, in combination, a fuse casing, acentrifugally actuated rotatable cylindrical detonator holder mountedtherein, a detonator mounted diametrally in said holder in safeposition, an axial detonator firing pin in restraining engagement withsaid holder, safety means for maintaining said firing pin in saidrestrainng engagement, and spring means adapted to act on said firingpin to advance said firing pin from said restraining engagement to armedposition after the fuse is fired in a projectile.

2. In a fuse for rotative projectiles, in combination, a fuse bodyhaving an axial cavity, a centrifugally rotatable cylindrical detonatorholder rotatably mounted in said cavity, a nose piece mounted on saidbody, a detonator firing pin axially mounted in said nose piece in safeposition, a detonator diametrally mounted in said holder and normallymaintained in safe position by said firing pin and rotor, and firing pinarming means adapted normally to maintain said firing pin in safeposition and on firing of the projectile automatically to release saidfiring pin and immediately after firing to move it into firing position.

3. In a fuse of the class described, in combination, a head strikerdetonator firing pin, a centrifugally actuated cylindrical detonatorrotor carrying a detonator normally maintained in safe position by saidfiring pin, and firing pin arming means actuated on firing in a gun torelease said firing pin, and after firing to advance said firing pin toarmed position, thereby to release said rotor and to permit saiddetonator rotor to rotate said detonator to armed position.

4. In a fuse for a rotative projectile, a selfaligning and self-lockingcentrifugally actuated detonator safety rotor comprising a cylinderhaving a central diametral bore and rotatably mounted with its axistransverse to the axis of the fuse, a cylindrical detonator mounted insaid bore with its axis oblique to the axis of rotation of the fuse, andmeans including a passage in said rotor extending parallelly withrespect to the axis of said detonator for generating angularly limitedtorque responsively to centrifugal force resulting from the spin of theprojectile in flight, thereby to rotate said detonator from safe toarmed position and to maintain the detonator in armed position.

5. As an article of manufacture, a centrifugally actuated detonatorsafety rotor having torquecouple masses for use in rotative projectilefuses comprising a cylindrical member with a central diametralcylindrical hole adapted to contain a detonator capsule, and at leastone passage in said cylindrical member disposed substantially parallellyto said hole, thereby to produce a torque-couple responsively tocentrifugal force acting to rotate said member about its axis.

6. In a detonating fuse for rotative projectiles a centrifugallyactuated detonator safety rotor comprising a rotatable member having acentral diametral bore adapted to carry a detonator capsule and havingintegral means for producing torque acting to rotate said member toarmed position responsively to centrifugal force, said means comprisingsymmetrical masses formed by at least one passage extending diametrallyacross said member in a direction substantially parallel to saiddiametral bore.

7. In a detonating fuse for rotative projectiles, a centrifugallyactuated safety rotor comprising a cylindrical member having a centraldiametral bore adapted to carry a detonator capsule, and also havingintegral means for producing a torque-couple responsively to centrifugalforce, said torque-couple acting to rotate said member about its axis toarmed position, said means comprising lands formed by a groove extendingdiametrally across the end of said member in a direction substantiallyparallel to said bore.

HARRY J. NICHOLS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,316,607 Watson Sept. 23, 19191,561,687 Brayton Nov. 17, 1925 1,774,043 Summerbell Aug. 26, 19302,155,100 Scelzo Apr. 18, 1939 FOREIGN PATENTS Number Country Date505,055 France Apr. 28, 1920 687,004 France Apr. 22, 1930 809,246 FranceDec. 3, 1936 837,467 France Nov. 12, 1938

